Whereas previous work on the self and relationships has focused exclusively on people's representations of self (i.e., the ME;), the work proposed here focuses on the role that the subjective experience of self (i.e., the I;) plays in people's relationships. Specifically, this application examines the phenomenon of I-sharing - the belief that one shares a phenomenological experience with another person - and the power it has to ease feelings of existential isolation and make us feel close to others. The 15 studies proposed employ a wide range of methodological techniques (most of them experimental, some of them quasi-experimental) to study the influence that I-sharing and existential isolation play in our relationships with others, including the relationships that stigmatized individuals form with outgroup members, and in our ability to be ourselves. Given the impact that existential isolation has on our psychological well-being, as well as on our ability to feel interpersonally connected, this research will offer insight into how people in the mental health profession can help clients dealing with issues pertaining to existential isolation, belonging, and belief certainty. In addition to having implications for the mental health of individuals, the work proposed here could have important implications for the quality of people's relationships. If the desire to I-share underlies people's preference for similar others, we will have identified a key to promoting more satisfying and harmonious interpersonal relationships. Whether we aim to repair relationships at the interpersonal or intergroup level, work on the importance of validating people's selves-as-subject (either because of I-sharing or through active efforts) shows us one potentially highly effective way to achieve that goal. In a world inhabited by people who kill themselves and one another over group differences, any insight we can gain into how to foster peace between people will be well worth our efforts.